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authorAndi Kleen <ak@suse.de>2005-09-12 18:49:24 +0200
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-12 10:49:56 -0700
commit673242c10d535bfe238d9d8e82ac93432d35b88e (patch)
tree959b4ffb0ebf788df812fe27498248c26610d22c
parenta54e678b8f476d6f28e6aa4409f6b88ce476af1b (diff)
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[PATCH] x86-64: Make lockless machine check record passing a bit more robust.
One machine is constantly throwing NMI watchdog timeouts in mce_log This was one attempt to fix it. (AK: this doesn't actually fix the bug I'm seeing unfortunately, probably drop. I don't like it that the reader can spin forever now waiting for a writer) Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/x86_64/kernel/mce.c32
1 files changed, 21 insertions, 11 deletions
diff --git a/arch/x86_64/kernel/mce.c b/arch/x86_64/kernel/mce.c
index 8aa5673..87ea8fd 100644
--- a/arch/x86_64/kernel/mce.c
+++ b/arch/x86_64/kernel/mce.c
@@ -56,15 +56,19 @@ void mce_log(struct mce *mce)
smp_wmb();
for (;;) {
entry = rcu_dereference(mcelog.next);
- /* When the buffer fills up discard new entries. Assume
- that the earlier errors are the more interesting. */
- if (entry >= MCE_LOG_LEN) {
- set_bit(MCE_OVERFLOW, &mcelog.flags);
- return;
+ for (;;) {
+ /* When the buffer fills up discard new entries. Assume
+ that the earlier errors are the more interesting. */
+ if (entry >= MCE_LOG_LEN) {
+ set_bit(MCE_OVERFLOW, &mcelog.flags);
+ return;
+ }
+ /* Old left over entry. Skip. */
+ if (mcelog.entry[entry].finished) {
+ entry++;
+ continue;
+ }
}
- /* Old left over entry. Skip. */
- if (mcelog.entry[entry].finished)
- continue;
smp_rmb();
next = entry + 1;
if (cmpxchg(&mcelog.next, entry, next) == entry)
@@ -404,9 +408,15 @@ static ssize_t mce_read(struct file *filp, char __user *ubuf, size_t usize, loff
}
err = 0;
- for (i = 0; i < next; i++) {
- if (!mcelog.entry[i].finished)
- continue;
+ for (i = 0; i < next; i++) {
+ unsigned long start = jiffies;
+ while (!mcelog.entry[i].finished) {
+ if (!time_before(jiffies, start + 2)) {
+ memset(mcelog.entry + i,0, sizeof(struct mce));
+ continue;
+ }
+ cpu_relax();
+ }
smp_rmb();
err |= copy_to_user(buf, mcelog.entry + i, sizeof(struct mce));
buf += sizeof(struct mce);